A conventional video decoder may utilize field identification (ID) information in order to properly decode a progressive and/or an interlaced video signal, for example. An interlaced video signal may be characterized by two field ID values, a zero and a one, for example. Each interlaced video frame may be decoded in two parts and each part may be characterized by a specific field ID value. The zero field ID value may be associated with a top part of an interlaced video frame, and the one field ID value may be associated with a bottom part of the interlaced video frame. The top part of a decoded interlaced video frame may be transmitted first and the bottom part of the decoded interlaced video frame may be transmitted second. In this way, a video decoder may receive alternating field ID values, which are characteristic of a top or a bottom part of a decoded interlaced video signal frame.
A progressive video signal frame may be decoded in its entirety with only one pass. A progressive video signal, therefore, may be characterized by only one field ID value, a zero or a one, for example. Receiving the same field ID values for a specific video signal may indicate, therefore, that a progressive video signal is being decoded by a video decoder.
Field ID detection may be obtained in a video decoder by comparing the timing relationship between the horizontal (H) and vertical (V) synchronization pulses. In order to enhance the accuracy of the field detection process, the information about the phase of the color subcarrier may be incorporated in the decision making process. In a noisy environment, the information obtained during any given single measurement of the field ID may be inaccurate and may cause a very specific distortion of the image, which may be referred to as a field swap. For example, a field swap may occur if the video decoder is decoding an interlaced video signal. In this case, instead of receiving alternating field ID values associated with a top and a bottom decoded video frame, the video decoder may start receiving the same field ID value. Various techniques, such as field ID phase lock loops (PLLs) and sophisticated signal processing of the incoming signal, for example, may be utilized to avoid undesired field swaps. This may complicate the implementation of the video decoder and may increase the number of gates in the silicon, for example, as well as the overall power consumption of the device.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.